1. Field of the Invention
The present invention relates generally to an outboard motor with a turbocharger and, more particularly, to a marine propulsion system in which a turbocharger is disposed above most of, if not all, of the cylinders of an engine in which the cylinders are vertically distributed and, in certain embodiments of the present invention, the turbocharger is located at a rearward portion of the engine above all of the cylinders.
2. Description of the Related Art
Turbochargers are well known by those skilled in the art for use in conjunction with internal combustion engines. Exhaust gases are used to drive a turbine which is connected in torque transmitting relation with a compressor. The compressor provides pressurized charge air that is used, within the cylinders, in the combustion process. Turbochargers are also known to those skilled in the art for use in conjunction with marine propulsion systems, including outboard motors. The patents described immediately below illustrate various types of turbochargers used in both marine applications and non-marine applications. Some of these patents are intended for use in conjunction with outboard motors.
U.S. Pat. No. 3,998,055, which issued to Bradford et al. on Dec. 21, 1976, describes a turbocharger for marine engines. It includes a dual chamber block interposed between a carburetor and a turbocharger. The block includes a first chamber for receipt of a fuel air mixture and a second chamber separated by a heat transfer wall from the first chamber. The second chamber receives hot water from the cooling system of the engine and effectively directs heat through the heat transfer wall to prevent condensation of fuel from the fuel air mixture in the first chamber. Consequently, it is possible to use a rich air fuel mixture and maintain the mixture in a vaporized state to prevent premature detonation and deterioration of the engine.
U.S. Pat. No. 4,760,704, which issued to Torigai on Aug. 2, 1988, describes a multi-cylinder engine with a turbocharger. It describes two-cycle, turbocharged internal combustion engines which have improved arrangements for locating the inlet of the turbine stage so as to minimize the necessity for backflow in the exhaust conduit. This system is described in conjunction with outboard motors and, in certain embodiments, with twin turbochargers. The turbochargers are disposed in such a relationship so as to permit a compact relationship and to avoid close proximity between the exhaust conduit and the compressor stages.
U.S. Pat. No. 4,827,722, which issued to Torigai on May 9, 1989, describes an engine of a turbocharger for an outboard motor. The engine is provided with a plurality of carburetors that draw air through a common plenum chamber. The turbochargers deliver pressurized air to the plenum chamber and an inner core is formed in the plenum chamber by having a heat exchanger extending across the plenum chamber. The inner core is cooled by circulating engine coolant through it.
U.S. Pat. No. 5,261,356, which issued to Takahashi et al. on Nov. 16, 1993, describes an outboard motor. A supercharged outboard motor includes a water cooling jacket that encircles the supercharger and also the duct which interconnects the supercharger with the engine for cooling of the supercharger and compressed air charge without necessitating a separate intercooler.
U.S. Pat. No. 5,293,846, which issued to Takahashi on Mar. 15, 1994, describes a two-cycle engine for an outboard motor. The outboard motor includes a supercharged internal combustion engine. The supercharger is positioned on a side of the crankcase opposite from the cylinders of the engine and is driven by the crankshaft through any of a plurality of different forms of drive arrangements that permit axial adjustments to maintain alignment.
U.S. Pat. No. 6,032,466, which issued to Woollenweber et al. on Mar. 7, 2000, describes a motor assisted turbocharger for an internal combustion engine. An efficient and reliable motor assisted turbocharger includes an assisting electric motor, a combination flow turbine wheel which may be inserted and removed from the turbocharger assembly through the exhaust opening of the turbine casing, and a divided volute turbine casing designed in a unique way so that the tips of the turbine blades can be extended to be closely adjacent to the turbine casing divider wall without complicating the mechanical design of the turbine, thereby providing an economical assembly with high turbine efficiency compared with conventional, radial turbines used in turbochargers.
U.S. Pat. No. 6,405,692, which issued to Christiansen on Jun. 18, 2002, discloses an outboard motor with a screw compressor supercharger. The screw compressor provides a pressurized charge for the combustion chambers of the engine. It has first and second screw rotors arranged to rotate about vertical axes which are parallel to the axis of a crankshaft of the engine. A bypass valve regulates the flow of air through a bypass conduit extending from an outlet passage of the screw compressor to the inlet passage of the screw compressor.
U.S. Pat. No. 6,408,832, which issued to Christiansen on Jun. 25, 2002, discloses an outboard motor with a charge air cooler. The charge air cooler is used in a preferred embodiment and the bypass conduit extends between the cold side plenum of the charge air cooler and the inlet of the compressor. The charge air cooler improves the operating efficiency of the engine and avoids overheating the air as it passes through the supercharger after flowing through the bypass conduit. The bypass valve is controlled by an engine control module in order to improve power output from the engine at low engine speeds while avoiding any violation of existing limits on the power of the engine at higher engine speeds.
U.S. Pat. No. 6,409,558, which issued to Gokan et al. on Jun. 25, 2002, describes a turbocharged engine structure for small sized boats. An engine is provided with an exhaust manifold and is disposed such that a crankshaft thereof extends in forward and rearward directions of a boat body, and an exhaust gas turbocharger which is driven to rotate by exhaust gas from the exhaust manifold is provided rearwardly of and adjacent to the exhaust manifold and rearwardly of and to adjacent to the engine. The exhaust gas turbocharger is disposed such that a shaft which connects a turbine and a compressor is directed in leftward and rightward directions of the boat body, and the turbine is disposed adjacent to the exhaust manifold and the compressor is disposed adjacent to an intake port of the engine. An intercooler is provided sidewardly of the compressor and disposed below an intake chamber.
U.S. patent application Ser. No. 10/965,524, which was filed by Augspurger on Oct. 14, 2004, describes a fluid cooled marine turbine housing. A method for reworking a corroded turbine housing for a turbocharger of a marine engine so that the corroded housing may be restored and reused is described. A turbine housing includes a central aperture for containing a turbine blade assembly and directing exhaust gases past the turbine blades in a turbocharger. The central aperture of a used turbine housing often is corroded such that the central aperture is enlarged and allows significant leakage. The corrosion may be removed and the aperture enlarged to receive an insert.
U.S. Pat. No. 7,189,005, which issued to Ward on Mar. 13, 2007, describes a bearing system for a turbocharger. The system is simple in design and easy to manufacture and has desired rotational dynamics of a three piece bearing design yet also has the superior vibration damping characteristics of a one piece bearing design. The inboard end of each journal bearing includes an axial recess for receiving an outboard end of a cylindrical bearing spacer, thereby axially locating the journal bearings as well as axially and radially locating the bearing spacer.
U.S. patent application Ser. No. 11/600,825, which was filed by Wizgall et al. on Nov. 17, 2006, describes a V-engine having at least one turbocharger. The engine also has at least two cylinders, and is constructed as a diesel engine and as an outboard motor for aquatic vehicles and wherein an exhaust to gas system leading from the minimum of two cylinders to the minimum of one turbocharger is arranged in the interior of a V formed by the cylinders. A vertically arranged crankshaft, cylinder heads which are designed to fold over, and coolant circuits supplied with seawater may also be provided in the V-engine.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
When turbochargers are used in marine applications, particularly in outboard motor applications, several additional problems must be addressed that do not normally occur in automotive or other non-marine applications. One problem relates to the limited space available for components, such as turbochargers, under the cowl of the outboard motor. Another problem relates to the potential inversion of water, from a body of water on which the marine vessel is operated, during certain conditions when internal pressures within the exhaust system and cylinders can induce the upward flow of water in a reverse direction through the exhaust system and toward the cylinders. In addition to the potential damage that this type of water inversion can cause to the engine, it can also draw water into and through the turbocharger and result in serious damage to the operability of the turbocharger. Therefore, it would be significantly beneficial if an outboard motor could be provided with a turbocharger in such a way that the turbocharger could be appropriately packaged under the cowl within the accommodating space and also reduce or inhibit the likelihood of damage in the event that water is drawn upwardly in a reverse direction through the exhaust system.